Question

var regxp = /[\S]/; //any char, not sure if it's /.*/ or something else
var obj = {
 atr1: "bla"
}
var blahs = obj[regxp]; //returns atr1

I’m looking for a shortcut to get methods/properties names from an object, because for..in is slow compared to a for loop for instance.
I want this for a special case when I know the object will have only one method/property

Answer 1

Yes, you can try to access a property of an object using a regular expression but no, it won’t do what you want: it will convert the regex into a string and use that property name.

The only way to find a property name on an object by matching a regular expression is a for ... in loop, like you mentioned. The performance should not be an issue if the object has only one property.

function findPropertyNameByRegex(o, r) {
  for (var key in o) {
    if (key.match(r)) {
      return key;
    }
  }
  return undefined;
};
findPropertyNameByRegex(obj, regxp); // => 'atr1'